1. Field of the Invention
The present invention relates to a color calibration system for a display device.
2. Description of the Background Art
In order for color matching in a visual environment, conventionally, color calibration for a display device has been performed by using a colorimeter. In a background-art color calibration system, a user performs an adjustment operation using a preset white point (luminance, chromaticity) or a user-desired white point as a target value. In the color calibration system, it is necessary for the user to adjust in advance various conditions which cannot be managed by a display itself, such as a color temperature and illuminance of lighting and color of paper in the visual environment.
Illumination light and a display of the display device are different from each other in shape of spectral distribution of observed light. Therefore, even if use of a dedicated colorimeter causes respective colorimetry values in tristimulus values of the CIE XYZ color space and the like to agree with each other between the illumination light and the display of the display device, actual visuals do not necessarily coincide.
For this reason, the user repeats calibration several times with a target value set by using limited information and tools, to make color matching in the visual environment. In the above-discussed color calibration system, since an optimal adjustment target value in accordance with the environment is uncertain, it is difficult to make accurate color matching. In other words, in the above-discussed color calibration system, it is extremely complicated and difficult to make color matching. A solution for this problem is shown in, for example, Patent Document 1 (Japanese Patent Application Laid Open No. 2006-349835).
In the technique of Patent Document 1, colorimetry of a reference object having reference white, which is irradiated with ambient light, is performed by using a colorimeter. A colorimetry result obtained by the colorimeter is a target value for color calibration.
In the technique of Patent Document 1, depending on white reference objects, in some cases, there is a difference in reflectance and spectral distribution, and generally, the spectral distribution of the white reference object is greatly different in shape from that of a monitor. For this reason, even if color matching is performed by using a colorimetry result obtained by a dedicated colorimeter, accurate color matching can not be necessarily achieved.
Further, in order to continue stable color calibration, it is necessary to always control the reference object. Colorimeters capable of performing colorimetry on an object color are limited, and a cheap contact-type colorimeter cannot perform accurate colorimetry in some cases.
In other words, the technique of Patent Document 1 has a problem of precision of color calibration and that of difficulty in achieving the color calibration.
For stable calibration, it is important that the display state of luminance, tint, and the like of the display device of which the power supply is repeatedly turned on and off irregularly should be stable during the calibration. It is very difficult, however, for the user who is an operator of the color calibration to grasp a stable state of the display device.